If two tornadoes collide, would they produce a stronger tornado?

[Kaivaira H]

6 months ago on Reddit, I asked how powerful tornadic winds would need to be to destroy above-ground storm shelters. In it, I explained that I was planning to do a rewrite of the 2014 movie, Into the Storm, to make it, among other things, more meteorologically accurate. In the film's climax, two large tornadoes collided with each other and turned into an even larger, more powerful super-tornado.

This isn't the first time I've heard of such a phenomenon: as far as I understand, in most instances, this occurs when the stronger member in the same tornado family ends up absorbing the smaller, often dying member. However, I haven't come across a definitive answer as to whether the combining of two funnels can make a tornado even stronger, which is what I'm hoping to get here.

The answers to this will go into the making of my story, which I will provide a quick explanation of.

At the time of that last post, I was debating whether or not I should split the story into two parts: one which was simply a better written version of the original movie but without any mega tornado at the end, and then the second part which would incorporate said-mega tornado in the worst-case scenario of one hitting a metropolitan city; or, if I should basically just combine both parts into one story.

I've since decided to go with the latter, though I will still be taking care to incorporate as many realistic elements as possible.

One being the actual tornado season. I have no interest in going down the now cliché route of making a fantasy storm season which culminates in the biggest tornado ever seen, as with films such as the original Twister, Into the Storm itself, the newly released Supercell, and almost certainly the upcoming Twisters. Instead, this story will be set in the 2014 storm season (since that's when the movie presumably takes place, as that was the year it was released) which was notoriously one of the most inactive seasons in years.

The story will culminate with the Pilger, Nebraska twins, that I have determined to be the most prime candidates for the story's final, big bad tornado. They were twins from the same storm, they destroyed a densely populated town, one reached EF4 strength while the other got up to EF3, and at one point, they collided with each other. All similar to the events of the movie.

Of course, I will be taking some creative liberties with this, in having the tornadoes collide as soon as they reach the town of Pilger, since in real-life they collided after passing it. Tragically, one person did die that day. Out of respect for them and their family, I will instead likely be offering up the fictional character Peter Moore and his tornado intercept vehicle, the Titus as a replacement, though if I do choose him, I still have yet to determine whether I will kill him off like in the movie or not. Once again, that, and the results of the twin tornadoes colliding with each other all rest on if two tornadoes combining will cause the wind speeds to skyrocket.

Thank you again for your time.

 

[Mark Gressman Jr]

Not really sure about the actual physics, but this might be as close to what you're envisioning as you'll find. Love me some vintage vids!

 

[Tony Laubach]

Here's a recent example I shot last week in Colorado where a satellite tornado and it's parent cone merged together; both ended up dying out within a minute of the merger.

 

[Jeff Duda]

Tony's video best shows what happens when two tornadoes approach each other.

Details:
1) I say "tornadoes that approach each other" because tornadoes rarely "collide" in the sense of like two cars colliding into a big wreck. Rarely will you have two tornadoes near each other moving at significant angles to each other. In nearly every situation, two tornadoes are on slightly different paths that merge together gradually.
2) Scientifically/mathematically, it's possible that the vertical vorticity in the two tornadoes could sum up, but since one of the merging tornadoes is almost always much smaller than the other (hence the reason they can merge in the first place), the total angular momentum that the smaller one contributes to the larger one doesn't increase the vorticity of the larger one by much.
3) A good visual depiction of merging tornadoes probably looks somewhat like model depictions of stars in space merging. They may near each other initially, but then begin to orbit each other. The mass sharing happens in a ribbon or strand between the two. That's probably pretty similar to how the vorticity of the absorbed tornado enhances that of the absorbing tornado. So it happens gradually and stringy rather than like two blobs of water or gel suddenly coalescing together.